Process for dewatering a proteinaceous, aqueous sludge and for removing and recovering precipitating agents from a precipitate containing proteinaceous substances

Abstract

A proteinaceous aqueous sludge, previously precipitated with a precipitating agent, is mixed with calcium chloride, and treated with a base selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides to adjust the pH to a value in the range of 6.5-9.5. The mixture is then heated to a temperature in the range of 60°-120°C. to coagulate and agglomerate the sludge, which is then separated from the aqueous phase containing the precipitating agent.

I claim: 
     
       1. A process for coagulating and agglomerating a proteinaceous aqueous sludge, previously precipitated with a precipitating agent, separating said sludge from the water therein contained, and recovering the precipitating agent comprising the sequential steps of; a. mixing said sludge with, calcium chloride   b. adjusting the pH to a value in the range of 6.5-9.5 by adding a base selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides,   c. heating said mixture to a temperature in the range of 60°-120°C in order to coagulate and agglomerate said sludge, whereby an aqueous phase containing the precipitating agent and a coagulated protein phase are formed, and   d. separating said aqueous phase containing the precipitating agent from said coagulated protein phase.   
     
     
       2. A process according to claim 1 wherein a heat coagulable protein selected from the group consisting of blood, comminuted meat and albumin also is added to the mixture in step (a). 
     
     
       3. A process according to claim 1 wherein said base is sodium hydroxide. 
     
     
       4. A process according to claim 1 wherein said base is calcium hydroxide. 
     
     
       5. A process according to claim 1 wherein said heating step (c) is carried out in two stages, by first preheating said mixture with agitation until the proteinaceous material begins to coagulate, and then forming a continuous stream of said precipitated mixture and heating the mixture rapidly to a temperature in the range of 60°-120°C by injecting steam into the stream of said preheated mixture. 
     
     
       6. A process according to claim 1 wherein said separated coagulated protein is washed with warm water. 
     
     
       7. A process according to claim 1 wherein said heating is carried out by injecting super-heated steam into the mixture. 
     
     
       8. A process according to claim 7, wherein said super-heated steam is injected into the mixture for a period of at least 2 minutes. 
     
     
       9. A process according to claim 1 wherein said separation step is carried out by centrifugation. 
     
     
       10. A process according to claim 9 wherein said heated mixture is cooled before the separation step is carried out.